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Digital
Signal Processing (DSP)
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DSP a crash course.
Digital signal processing is still a new technology and is rapidly developing. Basically DSP is the representation of a signal by a sequence of numbers. The numbers can then be manipulated or changed by a computing process to change or extract information from the original signal. Often this includes the extraction of noise for example. Bandpass shaping is another possible change that could be made. In fact using DSP we can even originate or create a signal from numbers in sort of a reverse process. One advantage of this is that there is no requirement for tuning as the signal is now just a sequence of numbers in the computer. This makes DSP a very stable and flexible way of dealing with electronic signals. Simple to sophisticated software is used to manipulate the numbers representing the original signal. New communications radios are now appearing on the market with DSP intermediate frequency processing making possible a multitude of IF filtering characteristics.
The following is a simple three step example of one possible use of DSP. It is an over simplification to be sure but the basic principles are what we are looking for at this point.
1. A/D Conversion. An input signal is first passed through a low pass filter and then digitized with an analog to digital converter. This is called sampling. Tiny separate samples are taken of the input analog signal and represented at that moment by a digital value. The higher the sampling rate (up to a point) the better we can reconstruct the original signal. However a sampling rate too high complicates our hardware, causes problems and isn't a good design practice. A compromise is always in order. So, what do we do with this digital signal that represents our original analog signal?
2. Signal Processing. Processing of the digital signal out of the A/D converter basically often consists of addition, multiplication, and delay. Addition and multiplication are very familiar terms and computers are very efficient at handling those operations. Delay refers to the ability of the processor to cause phase shifts, or comparisons of different parts of the signal and causing a change to take place in the output signal such as eliminating heterodynes of a particular frequency or wave shaping the signal. Here the process can and often does involve complicated higher order mathematics such as Discrete Fourier Transforms (DFT). This is a mathematical technique to determine the content of a signal mathematically. Other mathematical methods include the Inverse DFT (IDFT), the Fast Fourier Transform (FFT) and the Ztransform. All of these mathematical tools are used to manipulate our digital signal in special ways to produce the desired result. For example we may want to eliminate any specific impulse signals that may happen to come along, for example static crashes. We can also develop a variety of filters. One of these is called a finite impulse filter (FIR) or transversal filter. We are now too far into the process to go any farter and still keep it basic and simple. But at least you now have an idea of what is involved and know that the mathematical manipulation of a signal can get quite complicate and intricate. Programming of the DSP hardware requires a knowledge of higher mathematics and a knowledge of the DSP processor and the programming language it uses. Given all that knowledge we can do amazing things to the digital signal. That is the exciting power of DSP.
3. D/A conversion. The digital signal is now converted back to an analog signal complete with all the mathematically processed elements. It will not look like the original and that is the whole point we wanted to accomplish. We can use DSP to change a signal based upon our mathematically controlled manipulation.
How do you learn DSP? http://www.redcedar.com/learndsp.htm
A complete book on DSP free
online. http://www.dspguide.com/pdfbook.htm
The Scientist and Engineer's Guide to Digital Signal
Processing
By Steven W. Smith, Ph.D.
DSP LINKS
The following WWW links will take you directly to the various web site pages. Your browser URL address line will tell you the origin of the site. The links are to BERKELEY DESIGN TECHNOLOGY, INC. AND THE INDIVIDUAL CONTRIBUTORS. http://www.bdti.com
1.3 Where can I get free software for general DSP?
http://www.circuitsage.com/filter.html
Filter Design Articles
2. Michael Ellis' webpage: Includes a lot of detailed information on filters.
3. University of Oulo paper on CMOS Gm/C filters.
4. Tony Fisher's LC filter designer, an online tool for filter analysis.
5. A low sensitivity lowpass filter design tutorial by Kumen Blake.
6. Design of a 5th order butterworth SallenKey filter.
7. Greg's download page with some filter links.
8. A simple filter webpage with tooo much advertising.
9. Elliptical filter design by Cellestino Corral.
10. Analysis of the SallenKey filter by TI.
11. Filters for digital communication by TI.
12. Ian Purdie's notes on filter design.
13. Elliptical filter design by Celestino A. Corral.
15. Elliptical filter design by Philip Geffe.
16. Microwave filters lecture at Queens university.
17. NEC Research Index. Many articles on filter design.
18. ESSCIRC website. Many articles on filter design. Very good.
19. 1500 watt filter. Don't stand too close.
20.AARL's RF filter design website.
21. National's application notes 779: Introduction to Filters. 26: High speed active filters, 27: low sensitivity lowpass filter, 28: lowsensitivity bandpass filter, 29: low sensitivity highpass filter. 21: Predistortion for SallenKey filters.
22. Swarthmore article on active filters.
23. Maxim filter application notes.
24. FDI article on filter design.
25. RF Cafe article on filter transfer functions.
26. TI's filter wizard, for designing filters. and active filter application notes:
27. Ernie Kim's notes on microwave filter design.
28. Stanford class notes on microstrip filters.
29. Calvin Plett's analog course has some filter design information.
30. Many class projects on filter design at Berkeley.
Mathcad Filter Software
1. bpfloss.mcd: by Michael A. Earle, transmission and reflection properties of LC filters.
2. butter.zip: Low, high, and bandpass Butterworth filter simulator.
3. filter6.mcd: by D Weisner, a notveryhelpful delayline analysis.
4. hpfilter: by Roald C. Maximo, an LC Tchebyshev Highpass Filter designer.
5. lpfilter.mcd: by Roald C. Maximo, an LC Tchebyshev Lowpass Filter designer.
6. lpfsynth.mcd: by Roald C. Maximo, a more detailed LC Tchebyshev Lowpass Filter designer.
7. shntbpf.mcd, by Roald C. Maximo, Series Coupled Shunt Resonators Passive Bandpass Filters.
8. serbpf.mcd, by Roald C. Maximo, Shunt Coupled Series Resonators Passive Bandpass Filters.
9. synthact.mcd, by Roald C. Maximo, Synthesis of Active Filters.
10. Lance Lascari's edgecoupled bandpass filter designer in Mathcad.
11. Bill's active filter page.
12. FilterD, by Jacek Izydorczyk, zipped mathcad worksheets for filter design.
13. James Kang's mathcad filter routine. Check out all of his mathcad and matlab routines. Lot's of analog and digital filter routines.
14. Benhard Boser's filter design routines in Mathcad. This link also has a series of good lectures on analog circuit design.
15. Robert Hargar's Analog and Digital Communication Systems, a Mathcad book with lots of information on digital filter design and DSP.
16. Group delay for Butterworth BPF group_b.mcd, by Dave Peterson
17. A handy circuit for filter design unfltr6.mcd, by John Ellis
18. Corrugated microwave filter design corrfilt.mcd, by Rousslan Goulouev
19. Mathworks filter design routine's for MATLAB.
20. Download Mathcad Explorer Free, A free viewier for Mathcad versions 8 and lower. You can edit, but not save.
21. Mathcad Tutorial, a good tutorial by Sidney Young and Theresa Julia Zielinski.
22. Valery Ochkov's Book on Mathcad usage.
23. Information on Mathcad from Mathsoft.
24. James Kang's filter.mcd file. Extensive, but difficult to read.
25. Roald Maximo's synthact.mcd, an example active filter design.
25. Mathsoft's EE Handbook. Some basic filter design formulae.
25. Circuit Sage's sallenkey.mcd and pdf version. An extensive Mathcad 2001i routine for designing integrated SallenKey filters.
26. Circuit Sage's butter.mcd (pdf), ellip.mcd (pdf), and cheby.mcd (pdf) LC filter design routines.
Filter Design Software
1. S/FilSyn (PCFilt) from ALK Engineering: This PC demo version only works at one frequency, 833MHz (frequency translation is easy to do by hand, so the demo can easily be used for any design with a little thought!).
3. MicroSim Filter Designer Software: This PC demo version only allows up to third order filters to be designed. It has a great user interface. The full version is $750.
5. Interactive Filter Design Software: CGI script that finds filter poles and zeros and transfer function. Very similar to MATLAB's filter design routines (more analysis than synthesis).
6. filtorX: A simple filter design tool. I see no advantage over MATLAB. You also have to mail in an agreement to use it (too much work).
7. FilterMaster: A full working demo of Intusoft's filter design software. This isn't the real program, but a great demo:$2225, $335/year maintenance.
9. PCFilter, Active filter synthesis from Michael Ellis, $325, includes his book on filter synthesis.
10. University of Illinois Filter Synthesis Class. Some MATLAB routines for filter synthesis.
11. Max Froding's Butterworth Filter Synthesizer. Design 2 to 25 element Butterworth lowpass and highpass filters from your internet browser.
12. MIMICAD Filter Synthesis. A Commercial Filter Synthesis Tool. This webpage isn't very good.
13. FILTER  A free program for automatic synthesis of analog filters, by Bogdan Wilamowski.
14. LADDER (by Bogdan Wilamowski & Rob Koller)  A free program for synthesis of passive ladder prototype for analog and digital filter designs.
15. Serenade, Ansoft's Filter Synthesis Routine. I think it's cheap for universities.
16. superFILTER, Tatum Lab's Filter Design Software. Both digital and analog. Standard is $795 and Pro is $1995. It has a good simple demo. It's good, but it looks like it's topologies are limited.
17. FilterWiz, Standard is $89 (students$38), Pro is $199(students$84), A good cheap program with a good interface, but it's topologies are limited to biquads, which are more sensitive to process variations.
18. FaiSyn, A simple veryinexpensive filter design tool. It has limited capabilities, but it does the job for the right price: Corportate is $89, singleuser $35.
19. Adore, A module(opamps, switches, capacitors) generator for switched capacitor filters from Berkeley.Adore. $150 for distribution costs.
20. Eagleware's FILTER. $699 Eagleware has a complete suite of filter design tools including active and transmission line based tools, but charges another $699$999 for each product.
21. AADE Filter Design V 2.0, Looks nice, very inexpensive. $24.95.
22. Filter, Passive filter synthesis from Michael Ellis: Good, free DOS program.
23. Filter from Sherlab. Free DOS routine.
24. Wavecon Filter Designer, RF coupled line and tline filters. Demo available.
25. Filtershop,Analog and digital filter design software: $1500.
25. ScopeFIR, a free downloadable FIR design program.
26. AADE Filter Design, coupled resonator, crystal and LC filters, $24.95
27. IGOR digital filter design from Wave Metrics. $500.
28. Quickfil, active, passive and digital filter design. $2200.
29. Tunekit 2.0 by Max Froding.
30. Adlab, by Stephan Weber is a nice collection of circuit tools and has a nice user interface. $109.
31. Solorb's 2 pole bandpass filter calculator. Free, but very limited.
32. Filter3, A Free DOS routine by Jordan Strundjev for designing Chebyshev and Butterworth Filters.
33. Omicron's filter design tool, QuickFil, $2200.
34. Linear's FilterCAD, filter design tool. Free, but geared toward Linear IC's.
35. Arden Tech's Eclipse5 filter designer. $695.
36. RFShop's filter design spreadsheets and articles. Free.
37. eSeptum, a waveguide filter designer from engineers.com. $895.
38. Filter Workshop and Active Filter Workshop by Frank Ostrander. $80 each.
39. FNCElcad, a multipurpose circuit design tool with some active filters. $39.95
40. Filter Solutions, free trial, $50$1400 (depending on features)
41. Filtech, from numberone systems, $350.
42. Filtersyn(microstrip) and Cocafil(waveguide) filter design from Zelan.
43. TDS's collection of filter routines. $38.
44. Elsie, a filter design routine by Jim Tonne, $275, student version is free. He also has Helical, a helicalresonatorbased bandpass filter designer.
45. EPFIL, Waveguide filter design, by Djuradj Budimir, $279.
46. BASIC program to design Butterworth filters.
47. Thom Cuthbert's numerous BASIC programs for designing filters and matching networks. $10.
DSP LINKS
DSP Related Discussion Groups
Forward Concepts
International Telecommunication Union
Links to Embedded Systems Topics
Virtual Library of
Telecommunications Topics
Analog
Devices' DSP Newsletter
Analog
Devices' Motor Control Newsletter
Cahners MicroDesign Resources
Embedded Processor Watch
Texas Instruments News
Berkeley Design Technology Inc. 
benchmarks, DSP reports, optimization services for EEMBC
EEMBC (EDN Embedded Microprocessor Benchmark
Consortium)  Industrystandard, realworld benchmarks.
General DSP discussion
USENET newsgroup for discussing computer
benchmarks and publishing benchmark results and source code
LINKS
Other DSP, software, and mathematical resources
you may like can be found at:
A1A Jobs and Resources for Signal Processing
AC's
DSP Links
Adaptyv 
traitement du signal (France)
Armando
Cavero Miranda (Brasil)
ASU
Java Simulation Tool
Berkeley
Design Technology, Inc.
BIIB Tribus
(Canada  in French)
Cambridge
Engineering
Celestial
Chancellery (Russia)
Charles
Poyton's Filter Design Software Page
ChipCenter
 The Center of the Electronics Universe
Complex2Real
Computers
in Science and Engineering: CisePortal  DSP
CoopTel 
Cooperative de telecommunication (Canada  in French)
CrackingUniversity/Panorama
Electronics Links (Italy)
Cyber
City OnLine Electronics Net
DATASHEETS.COM
Department
of Electronic Systems, University of Westminster (UK)
DIGITALFILTER.COM
(Japan)
DJ2TK
DSP and
Communications Short Course
dspclips.com
DSPEngineering
Club (Yahoo!)  Digital Signal Processing
dspGuru
DSP
Interchange for Weaksignal Communication and SETI
DSPStore
(registration required)
EDN
Access
EE
Internet Resources
eetoolbox/eg3.com
 embedded, DSP, realtime and applied computing community portal
einSITE by
Cahners Electronics Group
ElecThai
(Thailand)
Electrical
Engineering Resources Page of the European Circuit Society (Denmark)
Electrical
World
electroclips.com
Electronic and
Electrical Engineering Communities of Southern Africa: Elektron EELinks
(Southern Africa)
elePARTS
(Korea)
Engineering
Central  engineering job site with resume database and special entry level and
CE/ChE/EE/IE/ME/Manuf. Eng pages
Engineering
Central Canada
ePanorama.net
 Best view to electronics in the Web
The
European Association for Speech, Signal and Image Processing (EURASIP)
Gap's
Website
Geometry.Net
 the Online Learning Center
Green Eggs
Report  Alice's Registry (Argentina)
Grundwissen
Elektrotechnik (Germany)
Hunt
Enginering  Real Time DSP Hardware (UK)
Ian
G. Clark's MiniPortal (UK)
International
Journal of Engineering Education (Ireland)
ISMRA
 Patrick Furon  Electronique, Numerique, Traitment du Signal (France)
Java
Skyline Online Magazine
Jinno's
DSP Links
Jonathan
G Campbell's WWW Links (Northern Ireland)
K5GP
Waterway CW Net Info
Leonel
Seabra de Sousa (Portugal)
Martindale's
Reference DeskCalculators Online Center
Mathtools.net.
M i c r o
S i n e (Thailand)
Micro
Technology Services, Inc
MusicDSP
Neil's
Digital Filter Page (UK)
Network
Cybernetics Corporation
New
Wave Instruments
Numerix
Ltd. DSP (UK)
Open
Directory Project  Electrical Engineering Software
ORFEUS
Seismological Software Library (Netherlands)
Pollak
Szentes  Pollack School of Electronics (Hungary)
Programmers
Heaven
Radio
Amateur Technology Society (Finland)
RadioTeknniikkaa
 Iipo J. Leppasen (Finland)
Real
Time Signal
researchdsp.com
 the Source for ADI DSP Based Research (UK)
ScenicRoute
Shareware
Music Machine (Australia)
ShareWire
Signal
Processing Information Base  Rice University
Stephan
Sprenger's DSP Dimension
Stray
Reed Laboratory (Japan)
Sverre
Holm's Java Signal and Image Processing (Norway)
Tahir
Ali (Indonesia)
TigerNut
PicInfo (Thailand)
Tutor Gig
UNL
Engineering Electronics Shop
Viperr's
Audio DSP Page and Links (South Africa)
Wavelets
and Signal Processing, Swinburne University School of Mathematical Sciences
(Australia)
WebEE  The
Electrical Engineering Homepage
WebEng by the
Universities of Strathclyde and Edinburgh (UK)
Web
World Index
OTHER LATE BREAKING SEMICONDUCTOR NEWS
Recommended books on DSP
Availability: Usually ships within 24 hours.
Hardcover (October 1996)
AddisonWesley Pub Co; ISBN:
0201634678 ; Dimensions (in inches): 1.24 x 9.54 x 6.48
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